Heisen
Forerunner
There is no repair in case of authorised apple service center, they mostly replace your device with a new one.One more point to consider is the repair charges after the warranty gets over.
I don't know about OnePlus but Apple products in general costs a lot to get repaired from authorised service centers.
If repair costs are not an issue then I would suggest to with iPad for the reasons others have mentioned.
This is the reason there are so many 3rd party repair services for apple devices.